Erm, first of all NEVER use wikipedia, it's a pile of poo! And monkeys probably write half the stuff on there;)

Second, it is classed as poorly water soluble, this is because it takes around 2000ml of water to dissolve 1g of Theobromine. It's called water-insoluble 'cos that's far above the amount it would require if it were water-soluble, however it's not technically 'insoluble'.

Thanks for the response tho,
I reckon it is something to do with pH...

Hah, I would but I don't know all the details of everything yet;) It's ok as a starting point, but should never be used for reference. It's not that I think it's rubbish in every aspect, but considering I could just go in there and change it with no knowledge on a subject...I think that says a lot about it's reliability:)

Anyway, thanks for advice everyone. Yes the question was about why it dissolves in acid and bases and not water. I think acids, bases and pH7 of water is a hint. Maybe it's because it's zwitterionic and needs a definite electron acceptor/donator. I think. The structure must have something to do with it, but I'm not entirely sure what...